The present invention relates to a method for the regeneration of a catalyst, in particular a zeolite containing titanium atoms which is used as a catalyst for the preparation of epoxides from olefins and hydrogen peroxide.
The preparation of epoxides from olefins by converting the olefin to the epoxide by means of hydrogen peroxide in the presence of a zeolite containing titanium atoms as catalyst is known (EP-A 0 100 119). M. G. Clerici, G. Bellussi and U. Romano , J. Catal. 129 (1991) 159-167 show moreover that the titanium-containing zeolite rapidly loses catalytic activity during its use as a catalyst for the epoxidation of propylene oxide. Clerici et al. describe two possible methods of regenerating the activity of the catalyst.
On the one hand the zeolite can be regenerated by calcining at 550.degree. C., on the other hand the catalytic activity can be restored by washing with solvents at elevated temperature, preferably with methanol or with the solvent used for the epoxidation. Regeneration by calcining has the disadvantage that for this purpose the catalyst has first of all to be dried, then heated to the high calcining temperature and subsequently cooled again, which results in a considerable additional energy requirement and expenditure for apparatus. Regeneration by washing with a solvent is a slow process, which as a rule requires considerably more time than the actual epoxidation reaction.
An object of the invention therefore is to find a method for the regeneration of a titanium containing zeolite catalyst which can be carried out quickly and easily.